Tuning the BMW N40B16

"Comprehensive guide to tuning and performance parts on the BMW N40B16 engine!"

The BMW N40B16 are awesome to work on and with carefully picked uprated upgrades like remaps, turbo upgrades and camshafts you will dramatically enhance your driving fun.

Let us review N40B16 tuning and provide tips on the best modifications.

Just because particular upgrades are appear in lots of N40B16 projects it doesn't mean it is good, instead we'll best upgrades that will give your N40B16 the best power gain for you money.

Significant gains on the N40B16 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the engines power and power output.

NB: Fast road camshafts tend to raise the bhp across the rev range, you may sacrifice a little low end bhp but your high end rpm power will be lifted.

Race camshafts, raise the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

On a typical daily driver must carefully try to optimize your power band to your driving style.

I'd never have found a N40B16 Motorsport and race camshaft is a pleasure to live with when on the daily commute.

Different N40B16 engines respond better to more or less aggressive camshaft durations than others.

The ECU mapping and fuelling also will make differences on the power gains you'll make.

Longer valve durations can alter the power band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Stage 1 modifications: Panel air filters, Fast road camshaft, Drilled & smoothed airbox, Sports exhaust manifold, Remaps/piggy back ECU, Intake headers.

Stage 2 modifications: fuel pump upgrades, induction kit, Fast road cam, Sports catalyst & performance exhaust, high flow fuel injectors, Ported and polished head.

Stage 3 modifications: Engine balancing & blueprinting, Competition cam, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves).

A remap helps unlock the full potential of all the modifications you've fitted to your N40B16.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved will differs on the modifications you've done and the condition of your engine.

It is the aim to any tuning job to feed air into the N40B16 engine

Intake transmit the air from the filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Structure and flow characteristics of the Intake can make a noticeable difference to to fuel mixing and power on the N40B16.

It's not uncommon that intake manifold are in dire need of aftermarket parts, although some makers provide decently flowing intake manifold.

Adding a N40B16 larger valve kit, doing a bit of N40B16 port enlargement and head flowing will also increase bhp, the fantastic side effect is it will afford you a greater bhp increase on other tuning parts.

Turbo upgrades

NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your N40B16

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes significant power gains.

When your car is turbo charged tuning mods are going to make more power and you'll see that turbo charged engines are made with better components.

However engines will have power limits

See where you'll find these limits and fit higher quality crank and pistons to handle the power.

It's not unheard of people spending a fortune on turbo charger upgrades on the N40B16 only to suffer the indignity of watching the engine throw a rod on it's first outing after it's been finished.

Large turbo chargers commonly suffer no power at low rpm, and smaller turbo chargers spool up more quickly but won't have the top end engines power gains.

Thankfully the choice of turbos is always moving on and we commonly find variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into a couple of channels and direct these at differently angled vanes in the turbocharger. They also help the scavenging effect of the engine.

You'll commonly see there is a limit in the air flow sensor MAP/MAF/AFM on the N40B16 when considerably more air is being pulled into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp and torque at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more challenging to setup. We have this feature on twinchargers if you want to read more.

Fuelling upgrades and mods

When you increase the power you will need to look at to the fuel system.

More power needs more fuel. It makes sense to be generous with your flow rate on the injectors.

As a rule of thumb add 20% capacity when fitting an injector, which takes into account injector deterioration and gives a little spare capacity should the engine need more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Exhaust upgrades and mods

Only look to increase your exhaust if your current exhaust is actually causing a restriction in flow.

On most factory exhausts you'll see the flow rate is ok even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts equal out the flow of gases through the engine.

But if the exhaust is too big, ie: over 2.5 inches bore, you will lose much of your flow rate and end up lacking power and torque.

Common exhaust restrictions can be located the catalysts installed, so adding a freer flowing high performance alternative will help avoid this restriction.

History of the Engine

DOHC four-cylinder petrol engine  replaced with the N45

• N40B16 114 bhp @6,100 rpm 150Nm(111 lbft) @4,300 rpm
  2001

Weak spots, Issues & common problem areas on the N40B16

The N40B16 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the N40B16, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your N40B16 engine please join us in our friendly forum where you can discuss tuning options in more detail with our N40B16 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under BMW. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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